Well I don't know.
Some people don't like to go through the process - fingerprinting and that dumb test that makes you think. A lot of people are too lazy to put an effort into it, like the guy I met today who was complaining that his company just terminated his lease because he refused to get one.
While others don't mind it. If you read the book you get at the DMV, go through the practice tests, you will pass it.
If you get four loads that pay say 15 cents more a mile and are more than 350 miles, then it pays for itself.
Again the diversity of the driver matters, or supposed to. If they have so-called "qualifications" that are "offered" by the company, they are supposed to be able to get more opportunities and so on. BUT with that said, the Hazmat endorsement is the easiest to obtain (among the gold star qualifications - high value, flat bed, Art, A&E, Rad, Special Shiny Rolling Advertisement Truck) and doesn't require raised letter invite by the company to obtain.
Now the other thing that comes to mind is sometimes the process adds a bit more to the driver's way of thinking. Maybe it is me but I become more aware of that Placard van driver who is cutting in and out of traffic than maybe I would have without knowing what the Placard meant.
And for you Van drivers, it is the trailer "van" not cargo vans so there!
Sorry if I sound like a smarta**, I am in one of them moods tonight - too many offers and no work today.